This invention relates to a spark timing controller for spark ignited internal combustion engines and more particularly to a spark timing controller that will ensure against stalling of the engine or erratic running under certain conditions.
As is generally known, the spark advance curve for an internal combustion engine follows a generally predictable pattern. That is, during cranking, idling and at low speeds the spark is provided with a fixed spark advance that is close to top dead center position. In some instances, this spark advance may be either before or after top dead center. Then as the engine speed increases, the spark advance is increased either along a straight or curved line until a maximum spark advance is reached. This maximum spark advance may occur before the maximum speed of the engine and the engine operates beyond this speed with a fixed spark advance. Of course, this type of spark advance curve is only a general description and specific engines vary within the general parameters set forth.
There are certain running conditions, however, wherein the conventional spark advance curve of the engine is not appropriate to the specific running characteristic. For example, it is the common practice with engines to employ some arrangement for reducing the speed of the engine under certain abnormal or senced conditions. For example, under conditions of emergency deceleration or upon abrupt interruption or reduction of engine speed for such reasons as engine protection in view of an abnormal running condition or to slow the speed of the engine to assist in shifting, the fixed spark advance curve may provide poor running. In addition, these conditions can, in extreme cases, cause stalling of the engine.
In the copending application of Kazumasa Ito entitled "Control Means of Internal Combustion Engine for Marine Propulsion", Ser. No. 229,942 filed Aug. 8, 1988 and assigned to the assignee of this invention, there is disclosed a spark advance system wherein poor running conditions and/or stalling are precluded by shifting the spark advance to a difference spark advance curve, normally an advanced curve, under such conditions. Although the systems disclosed in that application are particularly advantageous, they do require complicated circuitry and logic for their operation.
It is, therefore, a principal object of this invention to provide an improved spark timing control for a spark ignited internal combustion engine.
It is a further object of this invention to provide a spark timing control for a spark ignited internal combustion engine that is simple in construction, operation and principal and yet will prevent rough running or stalling under sudden deceleration conditions.
It is a still further object of this invention to provide an improved system for advancing the spark of an engine under extreme deceleration without necessitating complicated control logic.